I like the concept but looks odd because there are huge futuristic buildings but none of the city infrastructure like streets, squares, or other traffic areas. Add some more built environment in addition to the buildings themselves.

I can see you are importing the buildings and the terrain from separate models so you'll have a good amount of work in combining them to a good result. Work on the building models, extend some ground planes around the buildings for streets and traffic space and also model some separate generic road section you can clone and stretch between the separate building models. You can tidily end a building model to some sort of wall structure that should join neatly together with the terrain model.

As for the terrain model, it's a good background as it is but you could add some forest masses that extrude out of the terrain (like it was done in FFIX). The rivers should maybe be a bit different color than the sea, maybe tint them towards green or try to make the ocean tones deeper.